I love this extension for Chrome. Just found out that it has a Firefox version too, so I figured I'd share.
In short, this is what a new tab in Chrome looks like for me:
You can choose between Chrome-style screenshots for your bookmark icons, a set of included commonly used logos, or put in a URL to a logo of your choice. If you use a logo you've picked, the program automatically resizes it to fit on the icon, so it's pretty simple; bookmark a favorite site into Speed Dial, copy and paste a logo URL into the extension, and you're all set.
You can select from a series of color backgrounds, or add your own background image. For a while I debated using one of the amazing HDR photos from here: Gizmodo HDR Photo Shooting Challenge, but eventually chose to stick with a minimalist blue.
You can also adjust numbers of rows and columns, add the recently-closed items bar, and pretty much customize it as you see fit. A great way to make opening your favorite websites a visually-appealing one-click deal!
Speed Dial for Chrome
Speed Dial for Firefox